import java.util.Scanner;

public class Day_17_1_杨辉三角的变形 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()) {
            int n = sc.nextInt();
            if(n <= 2) {
                System.out.println("-1");
            }else if(n % 2 == 1) {
                System.out.println("2");
            }else if(n % 4 == 0) {
                System.out.println("3");
            }else {
                System.out.println("4");
            }
        }
    }
}
